What number systems can I convert between?

Binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16), plus fractions, decimals and percentages.

How do I convert any base to decimal?

Multiply each digit by the base raised to its position (0 on the right) and add them. Hex 2D = 2×16 + 13 = 45.

How do I convert decimal to another base?

Divide by the target base repeatedly and read the remainders from last to first. 45 ÷ 2 gives remainders 1,0,1,1,0,1 → binary 101101.

Number Converter

Quickly and accurately convert numbers between different formats, including binary, decimal, hexadecimal, and octal, making calculations and data conversions seamless for students, developers, and professionals.

Free
Instant results
Runs in your browser
Updated Sep 2026

In short

Enter a number, pick its base (binary, octal, decimal or hexadecimal) and the base you want; the converter shows the result instantly. For example, binary 101101 = decimal 45 = hex 2D.

How it works

Binary counts in base 2, octal counts in base 8. Converting means rewriting the same quantity with a different set of digits — the value never changes, only how it is written.

Convert each binary digit to its decimal value and add them up.
Divide that total by 8, keeping the remainders.
Read the remainders bottom to top for the octal result.

Shortcut: group the binary digits in threes from the right; each group is one octal digit.

The reverse conversion is Octal to Binary, which also handles every other base pair.

Examples

Worked examples, digit by digit:

10110 (binary) = 22 in decimal = 26 (octal)
101101 (binary) = 45 in decimal = 55 (octal)
11111111 (binary) = 255 in decimal = 377 (octal)

Common values in every base
Decimal	Binary	Octal	Hexadecimal
0	0	0	0
1	1	1	1
2	10	2	2
4	100	4	4
8	1000	10	8
10	1010	12	A
15	1111	17	F
16	10000	20	10
32	100000	40	20
64	1000000	100	40
100	1100100	144	64
255	11111111	377	FF

Number Converter: frequently asked questions

What number systems can I convert between?: Binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16), plus fractions, decimals and percentages.
How do I convert any base to decimal?: Multiply each digit by the base raised to its position (0 on the right) and add them. Hex 2D = 2×16 + 13 = 45.
How do I convert decimal to another base?: Divide by the target base repeatedly and read the remainders from last to first. 45 ÷ 2 gives remainders 1,0,1,1,0,1 → binary 101101.